1. Field of the Invention
This invention relates to devices used in the assay of a liquid sample. The device of this invention is suitable for use as a clinical diagnostic device in the measurement of the component of blood and urine and other substances.
2. Description of the Related Art
Known conventional devices used to assay of liquid sample are (1) assay devices for which filter paper is cut to a specified size, and is made to absorb the reagent that is to react with the sample, then the filter paper is attached to a support, and (2) assay devices for which gelatin containing the reagent is formed into a specified shape, then attached to a support. After preparing the assay device, the liquid samples are required to drop on the filter paper or the gelatin for assay.
The above-noted assay devices, however, require that the manufacturing process include the cutting and attaching of filter paper or gelatin. This does not allow refinement of the assay elements that hold the reagent, which, in turn, does not allow the miniaturization of the assay device as a whole, compared with its current form. Moreover, to enable the assay of a multiplicity of items using a single assay device, the above-noted conventional assay devices require the cutting and attaching of a multiplicity of filter paper or gelatins, thereby increasing the number of steps in the manufacturing process and increasing the manufacturing costs.
Therefore, the first object of this invention is to provide an assay device in which the assay elements that hold the sample have been refined. The second object of this invention is to provide an assay device manufactured with a multiplicity of assay elements, using few steps. The third object of this invention is to provide an assay device in which the detector and the part on which the sample is applied are separated from each other.
To achieve the objects described above, the liquid assay device of this invention comprises:
a support composed of an organic macromolecule, said support having a surface divided into two areas located adjacent to each other;
a divider in the surface, defining the border of both areas to separate a first area from a second area;
a detection layer affixed to the first area and containing a reagent; and
a water-swelling layer affixed to the second area, said water-swelling layer expanding by absorbing water.
To assay liquid samples using this device, a drop of the liquid sample is applied to the water-swelling layer. When the drop is applied, the water-swelling layer expands, extending over the divider and coming into contact with the detection layer. The liquid sample then moves by capillarity from the water-swelling layer to the detection layer, where it reacts with the reagent. If the reagent is such that it produces color or emits light when reacting to specific components, the components contained within the sample can be identified using optical methods. Depending on the properties of the reagent, other methods may also be used to identify components in the sample.
The detection layer of the device of this invention is separated from the location (the water-swelling layer) where the sample is dropped to, so when the sample is flowing from the water-swelling layer to the detection layer, a specific component within the sample can be removed from the sample. An example would be separating out the corpuscles when blood is being assayed. Moreover, a second reagent, that differs from the reagent contained in the detection layer, can be put in the water-swelling layer.
When the divider is composed of a water-repellent material, the reagent contained in the detection layer will not flow over onto the water-swelling layer until the reagent reacts with the sample, even if said reagent is a liquid.
A suitable method for manufacturing the device of this invention comprises the following steps:
(a) reforming the perimeter of a specific area on a surface of a support composed of an organic macromolecule so as to render it hydrophilic;
(b) forming a divider composed of a water-repellent material on the reformed perimeter;
(c) reforming the specific area and other area adjacent to the divider so as to render them hydrophilic;
(d) affixing a detection layer and a water-swelling layer to the reformed specific area and another reformed area respectively, said detection layer containing reagent, said water-swelling layer expanding by absorbing water.
This invention enables the refinement of the detection layer, by using the hydrophilic properties of the support to make a detection layer, a divider, and a water-swelling layer. Moreover, manufacturing costs are low, because there is no cutting and attaching work in the manufacturing process and a multiplicity of detection layers can be affixed simultaneously.